The present invention relates to refrigeration appliances and more particularly to a method for operating refrigeration appliances having multiple evaporators.
In typical domestic refrigeration appliances, the appliance oftentimes has two separate compartments which are maintained at different temperatures. For example, there may be a freezer compartment which has a temperature maintained below 0.degree. C. and a fresh food compartment which is maintained at a temperature somewhat above 0.degree. C.
In many commercially available refrigeration devices a single evaporator is used with an evaporating pressure of approximately 0-2 psig. Air is circulated over the evaporator from both the freezer compartment and the refrigerator compartment. This "mixed" air flow scheme results in dehumidification of the refrigerator compartment and subsequent frost build-up on the single evaporator coil, necessitating a periodic defrost cycle to get rid of the accumulated frost.
Also, using a single evaporator to provide the cooling for two compartments which are maintained at different temperatures results in an inefficient use of the refrigeration system for the higher temperature compartment.
It is known in the art to utilize multiple evaporators in refrigeration appliances. U.S. Pat. No. 2,576,663 discloses the use of two evaporators, each for its own refrigeration compartment. The evaporators are alternately supplied with refrigerant through a control valve.
U.S. Pat. No. 3,390,540 discloses the use of multiple evaporators in a refrigeration system. Each evaporator is controlled by an expansion valve and it is possible to operate more than one evaporator at a time.
U.S. Pat. No. 3,108,453 discloses a multiple evaporator refrigeration system in which the evaporators may be used independently of each other. Also a phase change material is used in connection with at least one of the evaporators.
U.S. Pat. No. 3,786,648 discloses the use of multiple evaporators for controlling the temperature in multiple compartments with the evaporators operating independently of each other.
U.S. Pat. No. 4,439,998 discloses a refrigeration apparatus having multiple evaporators with an electronically controlled valve system to deliver refrigerant to one evaporator in preference to the other, but causing the valve system to deliver refrigerant to the other evaporator after a predetermined amount of time.
U.S. Pat. No. 4,916,916 discloses the use of a phase change energy storage material in connection with a multiple evaporator refrigeration system.
Fuzzy logic controls are disclosed in U.S. Pat. Nos. 4,716,540 and 4,910,684.